Skin microdialysis coupled with laser speckle contrast imaging to assess microvascular reactivity

Laser speckle contrast imaging (LSCI) can be used to assess real-time responses of skin microcirculation to pharmacological interventions. The main objective of this study was to determine whether intradermal or subdermal microdialysis fiber insertion, coupled with skin flux recording using LSCI, can be used to assess baseline cutaneous flux and the post-occlusive reactive hyperemic response. The microdialysis sites were compared to control area without microdialysis fibers.

One dermal and two subdermal microdialysis fibers were randomly inserted in the right forearm skin of six healthy volunteers. We performed consecutively tests of post-occlusive hyperemia, infusion of 29 mM sodium nitroprusside (SNP), local thermal hyperemia at 43°C and a second 29 mM SNP infusion at the end of the experiment.

Two hours after fiber insertion, cutaneous vascular conductances (CVC) at the subdermal fiber sites were not different from their respective control regions of interest, while at the dermal site CVC remained higher (0.48+/-0.15 versus 0.37+/-0.1 PU.mm Hg(-1), P=0.003). The peak CVC and area under the curve observed during post-occlusive reactive hyperemia were similar at all fiber sites and their respective controls. We observed a similar increase in CVC using 29 mM SNP infusion, 40 min local heating at 43°C, and their combination. Finally, physiological and pharmacological responses of the subdermal sites were reproducible in terms of amplitude, whether expressed as raw CVC or as % CVCmax.

We showed that studying skin microvascular physiological or pharmacological responses using inserted subdermal microdialysis fibers coupled with LSCI is feasible and reproducible, and provides two-dimensional information. This technique will be useful for future mechanistic studies of skin microcirculation.